Dispensers utilizing chemical propellants have been in widespread use for many years, and have been a very successful packaging system. However, in recent years evidence has been produced which indicates that many of the chemical propellants are or may be harmful to the user and/or to the environment. Thus, legislation has been proposed and passed in many instances, limiting or banning the use of many of the more commonly used chemical propellants, such as fluorocarbons and the like.
Additionally, handling and disposing of such dispensers poses a serious problem because of the danger of explosion created by the propellants. Further, due to the nature of such propellants, the dispensers must be constructed to withstand high internal pressures, and design of the containers for aesthetic reasons is thus limited. Moreover, the number of products which may be dispensed is limited because of incompatibility of the propellants with some of the materials to be dispensed.
Accordingly, in view of the above problems, there has been a great effort in recent years to develop a dispenser which does not require the use of the chemical propellants, but yet which will achieve the same or comparable performance characteristics as the propellant operated dispensers. For example, it is desirable to achieve a sufficiently high pressure to obtain proper atomization of the product being dispensed. Also, it is desirable in some instances to achieve relatively long duration or continuous discharge of material. Further, compatibility of the dispenser components with the material being dispensed is necessary and, in any device of the type with which this invention is concerned, the structure should be simple and economical to manufacture, assemble and operate.